This section introduces aspects that may be helpful in facilitating a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Future OFDMA-based Fourth-Generation (4G) cellular radio access technology families such as 3GPP's Long-Term Evolution (LTE) and 3GPP2 UMB or WiMax may support premium(=expensive) machine-to-machine (M2M) applications in niche areas but are not prepared to support a mass-market cost-efficient wide-area deployment of M2M communications due to the unique needs with regard to: high number/density of machine nodes (e.g. for sensor applications), ultra-low energy consumption, new communication patterns/Quality-of-Service (QoS) demands, ultra-low duty-cycles, highly directional and redundant information streams, and low cost/low complexity systems.
The term M2M communication/signal as used herein relates to communications which require transporting data from a huge number of devices/nodes with a comparatively low data rate (e.g. 10 kb/s or less) over large distances (10 km and more). It is expected that for this purpose, efficient cellular machine-to-machine communications will require radical changes starting from the air interface and from there working upwards, simply because of the unique low cost/low complexity requirements of M2M communications. In particular, there is little chance of success to reduce e.g. the cost/complexity/energy consumption of future OFDMA based RF/PHY/MAC stacks to the needs of M2M sensor applications. Thus, M2M communications will typically require a dedicated air interface.
However, existing standards with regard to machine-to-machine communications are not adequate: For example, short-range Zigbee-like standards (802.15.4 et al.) have only a limited range (typically less than 50 m) and operate in the unlicensed ISM spectrum, such that QoS cannot be guaranteed. Also, re-using the cellular air interface will have a strong impact on battery life (no good sleep states, heavy signal processing) and will result in high-complexity RF/PHY/MAC protocol stacks, as well as high costs per user.
It is an object of the invention to provide: a method for efficiently transporting a machine-to-machine, M2M, signal over an OFDMA-based wireless radio access network.